Clean water is becoming an increasingly scarce resource while the demand for clean water is continuously growing. As a result, wastewater treatment and water reuse is becoming ever more important due to the diminishing natural clean water resources. Currently, wastewater can be treated utilizing a variety of technologies (i.e., membranes, bioreactors, filters, chemicals, etc.) or a combination of technologies. In the case of residential wastewater treatment (i.e., sewage treatment), most often the wastewater is treated at a municipal wastewater treatment plant or at the residence using a septic system. For industrial applications, the wastewater is most often treated at a local municipal wastewater treatment plant or it can be treated using an onsite wastewater treatment plant.
Onsite wastewater treatment plants have gained in popularity as environmental regulations directed toward contaminate discharge limits have become more stringent. The reason for this trend is onsite wastewater treatment plants can be designed to treat the particular wastewater of that facility, whereas a municipal wastewater treatment facility may not have the technology to properly treat all the wastewater contaminants that are supplied to the facility, particularly contaminants from industrial wastewater. In fact, some municipal wastewater treatment plants will not accept an industrial wastewater stream when they know their treatment technology is not adequate. An additional benefit of onsite wastewater treatment plants is that the effluent from the plant often can be reused acting as an additional water source for the site.
Onsite wastewater treatment facilities do have some drawbacks, for example, they can require substantial upfront capital investment in addition to the ongoing operational and maintenance cost. Despite the substantial upfront capital investment, for some remote locations and particular industries onsite wastewater treatment is the only viable option because the cost of trucking the wastewater to an offsite treatment facility is cost prohibitive. For example, various mining and natural gas exploration/production activities often in remote locations use substantial amounts of water and create equally substantial amounts of wastewater. Hydro-fracturing is one of those mining and natural gas exploration/production activities that uses significant quantities of water and generates significant quantities of wastewater.
In hydro-fracturing, drilling of the well can involve injecting water, along with sand and a mixture of chemicals under high pressure into a bedrock/shale formation via the well. This method is often referred to as fracking or sometimes hydro-fracking, and is intended to increase the size and extend existing bedrock fractures. The process can involve pumping water into fractures at high pressure in order to create long fracture sand pack intersecting with natural fractures in the shale thereby creating a flow channel network to wellbore. Hydro-fracturing releases the gas trapped in the natural fractures or pores of the shale so it can flow up a pipe to the surface for capture and use.
The hydro-fracturing process can use up to several million gallons of water per well. Consequently, the hydro-fracturing process can draw millions of gallons of freshwater for use as source water, depleting the local clean water sources. The hydro-fracturing fluids which are injected into a well can contain chemicals that can be toxic to humans and wildlife. The flowback water, which is the fluid that comes back up after hydro-fracturing, can include the chemicals pumped in plus both non-toxic and toxic substances that may be present in the shale formation.
The potential environmental impact related to hydro-fracturing (i.e., ground water contamination, mishandling of wastewater, risks to air quality, etc.) has caused concern among regulatory agencies and governments. For example, France in 2011 became the first nation to ban hydro-fracturing. Accordingly, there is a need for greener more environmentally friendly drilling wells using the hydro-fracturing process, particularly, the treatment of the wastewater for reuse.
As discussed above, treatment of the wastewater from the well can be accomplished by transporting the wastewater to an offsite municipal wastewater treatment plant via a sewage system or by trucking. However, the location of the wells can be remote, therefore often no sewage system is available for transporting the wastewater and trucking of the wastewater to the treatment facility is feasible, but often not a practical option due to the cost. Furthermore, the municipal wastewater treatment plant may not have the capacity or technology required to properly treat the wastewater contaminants and if the treated water is to be reused onsite it must also be transported back. Consequently, onsite wastewater treatment is often the most advantageous option, particularly for remote well sites. However, as mentioned above a wastewater treatment plant can require a substantial capital investment and typically the wastewater treatment plant will only be needed for a month or two at an individual well site while it is treating the wastewater produced. As a result, making a substantial capital investment in a permanent treatment plant at an individual well site is not practical either. It is accordingly a primary object of the present disclosure to provide and describe a mobile wastewater treatment plant configured to be transported from well site to well site via ground transportation, using roadways, and designed to treat the well wastewater and produce an effluent that can be reused or safely discharged into local water supplies.
In consideration of the aforementioned circumstances, the present disclosure provides and describes a mobile mechanical vapor recompression (MVR) evaporator that can be transported to a well site and is configured to treat the wastewater and provide a reusable effluent. According to an embodiment of the present disclosure, this can achieved by a horizontal dual chamber vapor separator and horizontal forced circulation evaporator. It is understood that the use of a mobile mechanical vapor recompression evaporator system of the present disclosure is not limited to use for hydro-fracking wastewater, but can be used for contaminated well water, surface water, radioactive water, a large variety of wastewater, or the like in a variety of applications and industries, wherever “in situ” processing of these streams is required or preferred.